The present invention relates to a composition active as an algaecide and a herbicide. In particular, the present invention relates to a composition for use in aquatic environments to control algae and aquatic plants. As used herein, the terms "algaecide" and "algaecidal" are meant to be used interchangeably and/or in conjunction with the terms "herbicide" and "herbicidal". Similarly, the term "algae" is meant to be used interchangeably and/or in conjunction with the term "aquatic plants".
Various aquatic environments, such as ponds, lakes, rivers, and canals, are susceptible to excessive algae growth. Such growth is undesirable for a number of reasons. For example, the presence of algae can restrict the flow of water and circulation throughout a body of water, resulting in stagnation. Excessive algae can discourage boating, swimming, or other recreational use. Certain strains of algae can cause the build up toxic agents in lakes or rivers, rendering those bodies of water unfit for use as irrigation sources. And for ornamental bodies of water, such as fountains and fish ponds, the presence of algae is often simply unsightly.
Copper ions have long been used to control the growth of algae in aquatic environments. In early applications, copper ions were provided by dissolving copper sulfate in the target body of water. Although somewhat effective, copper sulfate is not chemically stable in water. The disassociated copper ions react with carbonates present in the water to produce an insoluble precipitate of copper carbonate. Not only are the precipitated copper ions no longer available to control the algae growth, but the precipitated carbonate which settles at the bottom of the treated body of water may be unduly toxic to desirable plants or animals.
More recently, chelated copper ions in complexed form have been used to treat algae growth. U.S. Pat. No. 4,324,578, which is incorporated herein by reference in its entirety, discloses a method of preparing such a copper complex. The described complex, which consists of copper ions chelated with monoethanolamine and triethanolamine, is useful in that it maintains the copper ions in solution even in the presence of carbonates, unlike copper sulfate. In addition, copper complexes such as those described in U.S. Pat. No. 4,324,578 have improved stability to both heat and light. Despite these advantages, however, complexed copper ions are easily diluted (or carried away by water flow) when applied directly to a body of water. As expected, dilution results in a loss of effectiveness because of decreased contact between the copper ions and the target algae.
To overcome this problem, copper complexes have been combined with a water-insoluble phase, using emulsifiers and wetting agents, to create an emulsion containing copper coordination complexes. Such emulsions enhance the uptake of copper ions from the aqueous solutions by the target algae or other plants. The enhancement is observed in terms of speed of the take-up and quantity of copper ions which penetrate into the physiological system of the organism. One such composition is described in U.S. Pat. No. 5,407,899, which is incorporated herein by reference in its entirety. U.S. Pat. No. 5,407,899 discloses an emulsion consisting of 42.5% by weight of a chelated copper complex, 12.7% by weight of an emulsifier (composed of 8.5% by weight of tall oil fatty acid and 2.7% by weight of triethanolamine), 42.5% by weight of d,1-limonene (a wetting agent and the principle ingredient of the water-insoluble phase), and 3.8% by weight of sodium xylene sulfonate (a surfactant). The emulsion described in U.S. Pat. No. 5,407,899 is commercially available as a product called CLEARIGATE.RTM.. Increased copper ion uptake has also been achieved by mixing commercially-available chelated copper complexes with separately-available emulsifier/wetting agent carrier compositions. For example, the well-known copper complex CUTRINE-PLUS.RTM. is often used in combination with CIDEKICK.RTM., a carrier composition that contains emulsifying agents and a large proportion of limonene.
There are a number of problems with these existing algaecidal formulations. To begin with, such formulations are flammable and tend to exhibit some toxicity to humans. The flammability is attributable to the presence of large amounts of terpene wetting agents such as limonene. Terpene wetting agents are characteristically highly flammable, and, as would be expected, algaecidal formulations containing large amounts of these agents are therefore also flammable. Increased terpene concentration also contributes to the toxicity of algaecidal formulations. For example, the presence of large amounts of limonene appears to contribute to the dermal toxicity of the algaecide described in U.S. Pat. No. 5,407,899 (which exhibits Category II dermal toxicity under 40 C. F. R. .sctn. 156).
The use of large amounts of terpene wetting agents in an algaecide is also expensive. Typical wetting agents such as limonene do not serve as active algaecidal ingredients and, therefore, the presence of large amounts of a wetting agent in a composition tends to displace the active algaecide (for example, the copper complex). As a result, the user must apply greater amounts of the composition to a body of water in order to obtain the desired level of copper to reduce algae growth. Not only is such use of an excess of wetting agent inefficient, it increases the cost of the algaecide.
Another disadvantage to existing algaecidal formulations is that they often contain conventional surfactants. As used herein, the phrase "conventional surfactant" refers generally to any known anionic, nonionic, or amphoteric surfactants such as sulfonates or ethoxylates, but excludes the terpene wetting agents and emulsifiers described herein, to the extent that such compounds may fall under a broad definition of the term "surfactant". The use of a conventional surfactant increases the cost of an algaecide twofold. First, the surfactants themselves tend to be quite expensive--even when added in small quantities. Second, the addition of a surfactant necessitates an additional processing step in the manufacture of the algaecide. Aside from cost issues, surfactants are problematic because they are toxic to certain species of fish. Due to this toxicity, algaecides containing conventional surfactants are unsuitable for use in certain aquatic environments.
An additional problem exists with algaecidal formulations that are prepared by mixing commercially available copper complexes with emulsifier/wetting agent carrier packages: the additional mixing step is costly and inconvenient for the consumer. This is the case with the CUTRINE-PLUS.RTM./CIDEKICK.RTM. mixture referred to above. Because these two products are immiscible, they must be manually agitated both prior to and during application to the target body of water. In practice, one person operates a spraying device to apply the algaecide, while another person continuously agitates the CUTRINE-PLUS.RTM./CIDEKICK.RTM. mixture that is being applied. Thus, successful application of this mixture requires either the use of an additional piece of equipment (i.e., an automatic mixing device), or an additional person's time.